title: Rad24 truncation, coupled with altered telomere structure, promotes cdc13-1 suppression in S. cerevisiae.
abstract: Distinguishing telomeres from DNA double strand breaks is critical for genome stability. In S. cerevisiae, the Cdc13 single-strand telomere binding protein is critical for protecting chromosome ends. The C-rich telomere strand is lost at high temperatures in cdc13-1 strains, leading to activation of the DNA damage checkpoint and cell inviability. Through a screen performed to identify activities involved in telomere C-strand loss, we identified two new rad24 alleles. Rad24 is an alternate Rfc1 subunit, functioning to load the 9-1-1 checkpoint clamp. In each rad24 allele, a transposon inserted within the RAD24 coding region leads to expression of different carboxyl-terminal portions of Rad24, deleting or truncating the amino-terminus. We show that an intact Rad24 amino-terminus is necessary for its checkpoint function. Interestingly, the initial cdc13-1 rad24-2 strains grew at 36 degrees C, but the extent of suppression associated with rad24-2 weakened in serial backcrosses, and cdc13-1 segregants from these crosses showed a modest increase in temperature resistance. Moreover, while a RAD24 plasmid suppressed the checkpoint defect in the initial cdc13-1 rad24-2 strain, the temperature resistance was only partially suppressed. These data suggest that the TG(1-3) amplification observed in this strain contributes to the suppression phenotype. By recreating the rad24-2 allele in a strain with normal telomeres, we find that, relative to the rad24-delta allele, rad24-2 increases the frequency of obtaining cdc13-1 cells capable of growth at high temperatures. Our hypothesis is that the Rad24-2 truncation protein affects telomere structure or recombination in a manner distinct from rad24-delta.
authors.affiliation: Department of Cell Biology and Neuroscience, University of California, Riverside, Riverside, California 92521, USA.
authors.forename: Vanessa Y
authors.initials: VY
authors.lastname: Small
authors.forename: Charles
authors.initials: C
authors.lastname: Chuang
authors.forename: Constance I
authors.initials: CI
authors.lastname: Nugent
mesh_terms: D000483:Alleles; D018797:Cell Cycle Proteins / Q000737:chemistry / Q000378:metabolism*; D049109:Cell Proliferation; D003433:Crosses, Genetic; D004277:DNA, Single-Stranded / Q000378:metabolism; D016153:Genes, Suppressor; D047908:Intracellular Signaling Peptides and Proteins / Q000737:chemistry / Q000378:metabolism*; D009154:Mutation / Q000235:genetics*; D012091:Repetitive Sequences, Nucleic Acid / Q000235:genetics; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics*; D013489:Suppression, Genetic; D016615:Telomere / Q000737:chemistry*; D034501:Telomere-Binding Proteins / Q000235:genetics*; D013696:Temperature
chemical_list: C452219:Cdc13 protein, S cerevisiae; D018797:Cell Cycle Proteins; D004277:DNA, Single-Stranded; D047908:Intracellular Signaling Peptides and Proteins; C088385:RAD24 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D034501:Telomere-Binding Proteins